Why? If he were not in Spurs’ plans this season, he could have gone elsewhere in England or Europe …

We will await Dempsey’s public comments, but after seven productive seasons in the Premier League, he was presented with the opportunity to return to America with his family at a high pay scale. This is, by no means, a pre-retirement transition. Dempsey, 30, returns at, if not his prime, close to it. Heck, just 15 months ago, he finished fourth in the English Football Writers’ Association voting for player of the year behind Robin van Persie, Wayne Rooney and Paul Scholes.

Dempsey instantly becomes the American face of not only his new club, but his new/old league. (Sorry, Landon.)

It’s not unusual for stars to go home after years abroad: In January 2011, at age 30, Ronaldinho returned to Brazil after 10 years with PSG, Barcelona and AC Milan. The level of play in Brazil is higher than MLS, but you get the point.

So how much money is involved in the transfer?

Several reports say the fee is $9 million. Is Seattle paying the entire amount or is MLS, which owns all player contracts, subsidizing the transfer in order to secure the return of a bonafide American star? Hmm. With expansion — and expansion fees — on the horizon, the league is eager to boost its value.

What is Dempsey’s salary?

Initial reports said $8 million per year guaranteed for four seasons — an astounding figure that would eclipse David Beckham‘s pay stub. I am told, however, his base is closer to $4 million guaranteed over four years, which would put him in the 2013 contract neighborhood of Robbie Keane, Thierry Henry and Tim Cahill. The MLS players’ union will not release an updated salary list until the fall.

The Revs received a transfer fee when he left for Fulham in 2007, ending ties with the player. Same deal if Andy Najar were to return to MLS someday: D.C. United has already been compensated for his departure and can no longer claim league rights. It’s a different situation for players who decline MLS offers to sign overseas. San Jose, for example, retained Clarence Goodson‘s rights for six years because he rejected their proposal after they selected him in the expansion draft. The Earthquakes were not compensated for his departure and were able to store away his rights for a rainy day (this summer).

How is Seattle able to acquire Dempsey?

Dempsey would appear to fall into this category:

“The allocation ranking is the mechanism used to determine which MLS club has first priority to acquire a U.S. National Team player who signs with MLS after playing abroad, or a former MLS player who returns to the League after having gone to a club abroad for a transfer fee.”

Seattle is second in the allocation ranking behind Portland. Presumably, the Timbers could not afford — or did not want to spend — a giant sum and decided to pass, allowing Dempsey to fall into arch-rival Seattle’s lap. Portland would retain the top position in the allocation order. What if the Timbers had claimed him and held his rights for ransom? Seattle would have had to give up players and money to complete the acquisition.

The procedures are not, however, clearly spelled out in MLS’s roster rules and regulations. There is also the question of whether Dempsey’s status as a designated player (someone set to earn more than $368,000) is exempt from the allocation process, even though he is a U.S. national team player.

In a nutshell, after 17 years, MLS’s acquisition rules are, in Winston Churchill‘s words, “a riddle, wrapped in a mystery, inside an enigma.”

UPDATE: MLS has issued a statement attempting to further explain acquisition guidelines. Dempsey was not subjected to the allocation process.

What does Dempsey do for Seattle, off the field?

The Sounders are already the biggest home draw in MLS, averaging 41,000 at CenturyLink Field (almost double the next best, the Los Angeles Galaxy). Over the long term, will Dempsey’s arrival push that figure even higher? I am skeptical. For all his qualities and appeal, Dempsey is not an international superstar that transcends the game. I would expect an initial bump at the box office but not a substantial sustained increase. Replica jerseys, on the other hand, will fly off the shelves.

Will the Sounders become the MLS Cup favorites?

Seattle struck at the right time: There are no great clubs in the league this year. Many very good teams, but no dominant sides. Twelve of the 19 clubs entered the weekend with between 30 and 37 points through 20 to 23 matches. For better or worse, that’s parity. The Sounders, who have never advanced to the final, see a chance to make a hard push during the final third of the regular season and into the playoffs. Currently seventh in the Western Conference, but just four points off the playoff pace, Seattle has raised its attacking profile.

Will Dempsey miss MLS games while on U.S. national team duty?

Assuming he is recalled for the World Cup qualifiers against Costa Rica and Mexico in early September, he will miss home matches against Chivas USA and Chicago. By the time the last two qualifiers in mid-October roll around — during the final weeks of the MLS regular season — the Americans may have already secured passage to the World Cup. In that case, most regulars would probably remain with their clubs.

Will U.S. Coach Juergen Klinsmann applaud Dempsey’s move stateside?

Doubt it. Klinsmann has emphasized the importance of his regulars playing at the highest levels — major European circuits as well as the Champions League and Europa League. In MLS, Dempsey will toil in a growing but middling league whose aspirations reach the CONCACAF’s unexceptional version of the Champions League.

On the flip side, Dempsey is guaranteed a full-time starting role in Seattle. That was not the case at Tottenham this season and not necessarily assured elsewhere in Europe. Oguchi Onyewu was with a La Liga side (Malaga) that advanced to the Champions League quarterfinals this past spring, but he sat and watched, and would have been better off playing regularly on a less successful team.

Looking ahead to the World Cup, Dempsey promises a fresher and healthier status than his former colleagues in Europe. While Euro-based players are bruised and exhausted ahead of international competition in the summer, MLS’s March-to-October calendar allows players to arrive at the World Cup in peak condition and form.

How will Seattle’s teammates take to Dempsey?

Clint is a good dude — well-liked and admired around U.S. soccer for both his skill set and work ethic. No issues there. He will lead and inspire. His enormous contract, though, could prompt some grumbling in the locker room. U.S. national team forward Eddie Johnson is earning $150,000 — not even one-tenth of teammate Obafemi Martins‘ deal and at least 28 times less than Dempsey’s salary. Will the latest move bruise Johnson’s ego? Beyond his coaching responsibilities, Sigi Schmid may need to become the team therapist.

How will Dempsey, a Texan who embraced soccer-mad London, take to the Emerald City?

Before the World Cup qualifier against Panama in June, he raved about the soccer vibe on the streets of downtown Seattle while the Sounders were playing nearby at CenturyLink. “I almost felt like I was in another country,” he said of his stroll through the city as people watched the league match on TVs in restaurants and bars.

Seattle plays on artificial turf, not the soft grounds of England …

Yes, Seattle plays of turf. Turf is not natural grass. Ideal for a veteran player? No. The game is different on turf, as well — the bounces, speed of play, impact on the body. Dempsey will need to adjust.

Here’s betting he conforms just fine.

Steven Goff is The Post’s soccer writer. His beats include D.C. United, MLS and the international game, as well as local college basketball.

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